The present invention relates to point to multi-point communications systems. More specifically, the present invention relates to a method and apparatus for reducing latency in waking up a group of dormant push-to-talk communication devices in a net within a group communication network
A class of wireless service intended for quick, efficient, one-to-one or one-to-many (group) communication has existed in various forms for many years. In general, these services have been half-duplex, where a user presses a xe2x80x9cpush-to-talkxe2x80x9d (PTT) button on his phone/radio to initiate speech. Pushing the button either keys his radio, in some implementations, or in a moderated system, where communications occurs via a server of some type, indicates the user""s request for the xe2x80x9cfloor.xe2x80x9d If granted the floor, or talker permission, the user then generally speaks for a few seconds, after which he releases his PTT button, and other speakers can request the floor. Communication is generally from one speaker to a group of listeners, but may be one-to-one. This service has traditionally been used in applications where one person, a xe2x80x9cdispatcher,xe2x80x9d needs to communicate to a group of people, such as field service personnel or taxi drivers, which is where the xe2x80x9cdispatchxe2x80x9d name for the service comes from.
Recently, similar services have been offered on the Internet and are generally known as xe2x80x9cvoice chat.xe2x80x9d These services are usually implemented as personal computer applications that send vocoder frames in Internet protocol (IP) packets, i.e., voice-over-IP (VoIP) service, to a central group chat server, or possibly from client to client in a peer-to-peer service.
A key feature of these services is that communication is quick and spontaneous, usually initiated by simply pressing a PTT button, without going through a typical dialing and ringing sequence. Communication in this type of service is generally very short, with individual talk xe2x80x9cspurtsxe2x80x9d being generally on the order of several seconds, and xe2x80x9cconversationsxe2x80x9d lasting possibly a minute or less.
The time delay between when the user requests the floor and when he receives a positive or negative confirmation from the server that he has the floor and may begin speaking, which is known as the PTT latency, is a critical parameter for half-duplex group communications systems. As mentioned previously, dispatch systems place a priority on short, quick conversations, which makes the service less effective if the PTT latency becomes large.
Existing group communication infrastructures provide limited opportunities for significantly reducing the PTT latency, i.e., actual PTT latency may not be possibly reduced below the time required to re-establish traffic channels within dormant packet-data sessions. Further, talker and listeners traffic channels are brought up in series, because the only mechanism available to begin waking up a dormant group is to wait for the talker""s traffic channel to be re-established to signal the server. Currently, no mechanism exists to send mobile-originated user signaling data on anything other than a traffic channelxe2x80x94a limitation that requires traffic channels to be re-established before any communication between clients and the server can take place.
There is a need, therefore, for mechanisms to reduce both apparent PTT latency experienced by the talker and total time required to re-establish traffic channels for participating mobiles without negatively impacting system capacity, client battery life, or other resources.
The disclosed embodiments provide a novel and improved method and apparatus for reducing dormant-wakeup latency in a group communication network. In one aspect of the invention, a method for reducing latency in a group communication network includes the steps of receiving a dormant-wakeup trigger directed to a target listener mobile, triggering the target listener mobile to re-establish a traffic channel, and storing the dormant-wakeup trigger for later transmission to the target listener mobile. In one aspect, the method further includes transmitting the stored dormant-wakeup trigger to the target mobile as soon as the target mobile has re-established a traffic channel.
In one aspect, an apparatus for reducing latency in a group communication network includes a memory unit, a receiver, a transmitter, and a processor communicatively coupled with the memory unit, the receiver, and the transmitter. The processor is capable of receiving a dormant-wakeup trigger directed to a target listener mobile, triggering the target listener mobile to re-establish a traffic channel, and storing the dormant-wakeup trigger for later transmission to the target listener mobile.